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/*

 * Copyright (c) 2008 Jakub Jermar

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/** @addtogroup fs

 * @{

 */ 

/**

 * @file	vfs_register.c

 * @brief

 */

#include <ipc/ipc.h>

#include <ipc/services.h>

#include <async.h>

#include <fibril.h>

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <ctype.h>

#include <bool.h>

#include <futex.h>

#include <libadt/list.h>

#include <as.h>

#include <assert.h>

#include <atomic.h>

#include "vfs.h"

atomic_t fs_head_futex = FUTEX_INITIALIZER;

link_t fs_head;

atomic_t fs_handle_next = {

	.count = 1

};

/** Verify the VFS info structure.

 *

 * @param info		Info structure to be verified.

 *

 * @return		Non-zero if the info structure is sane, zero otherwise.

 */

static bool vfs_info_sane(vfs_info_t *info)

{

	int i;

	/*

	 * Check if the name is non-empty and is composed solely of ASCII

	 * characters [a-z]+[a-z0-9_-]*.

	 */

	if (!islower(info->name[0])) {

		dprintf("The name doesn't start with a lowercase character.\n");

		return false;

	}

	for (i = 1; i < FS_NAME_MAXLEN; i++) {

		if (!(islower(info->name[i]) || isdigit(info->name[i])) &&

		    (info->name[i] != '-') && (info->name[i] != '_')) {

			if (info->name[i] == '\0') {

				break;

			} else {

				dprintf("The name contains illegal "

				    "characters.\n");

				return false;

			}

		}

	}

	/*

	 * This check is not redundant. It ensures that the name is

	 * NULL-terminated, even if FS_NAME_MAXLEN characters are used.

	 */

	if (info->name[i] != '\0') {

		dprintf("The name is not properly NULL-terminated.\n");	

		return false;

	}

	/*

	 * Check if the FS implements mandatory VFS operations.

	 */

	if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_LOOKUP)] != VFS_OP_DEFINED) {

		dprintf("Operation VFS_LOOKUP not defined by the client.\n");

		return false;

	}

	if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_READ)] != VFS_OP_DEFINED) {

		dprintf("Operation VFS_READ not defined by the client.\n");

		return false;

	}

	/*

	 * Check if each operation is either not defined, defined or default.

	 */

	for (i = VFS_FIRST; i < VFS_LAST_CLNT; i++) {

		if ((info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_NULL) && 

		    (info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_DEFAULT) && 

		    (info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_DEFINED)) {

			dprintf("Operation info not understood.\n");

			return false;

		}

	}

	return true;

}

/** VFS_REGISTER protocol function.

 *

 * @param rid		Hash of the call with the request.

 * @param request	Call structure with the request.

 */

void vfs_register(ipc_callid_t rid, ipc_call_t *request)

{

	ipc_callid_t callid;

	ipc_call_t call;

	int rc;

	size_t size;

	dprintf("Processing VFS_REGISTER request received from %p.\n",

	    request->in_phone_hash);

	/*

	 * The first call has to be IPC_M_DATA_SEND in which we receive the

	 * VFS info structure from the client FS.

	 */

	if (!ipc_data_write_receive(&callid, &size)) {

		/*

		 * The client doesn't obey the same protocol as we do.

		 */

		dprintf("Receiving of VFS info failed.\n");

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	dprintf("VFS info received, size = %d\n", size);

	/*

	 * We know the size of the VFS info structure. See if the client

	 * understands this easy concept too.

	 */

	if (size != sizeof(vfs_info_t)) {

		/*

		 * The client is sending us something, which cannot be

		 * the info structure.

		 */

		dprintf("Received VFS info has bad size.\n");

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/*

	 * Allocate and initialize a buffer for the fs_info structure.

	 */

	fs_info_t *fs_info;

	fs_info = (fs_info_t *) malloc(sizeof(fs_info_t));

	if (!fs_info) {

		dprintf("Could not allocate memory for FS info.\n");

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	link_initialize(&fs_info->fs_link);

	futex_initialize(&fs_info->phone_futex, 1);

	rc = ipc_data_write_finalize(callid, &fs_info->vfs_info, size);

	if (rc != EOK) {

		dprintf("Failed to deliver the VFS info into our AS, rc=%d.\n",

		    rc);

		free(fs_info);

		ipc_answer_0(callid, rc);

		ipc_answer_0(rid, rc);

		return;

	}

	dprintf("VFS info delivered.\n");

	if (!vfs_info_sane(&fs_info->vfs_info)) {

		free(fs_info);

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	futex_down(&fs_head_futex);

	fibril_inc_sercount();

	/*

	 * Check for duplicit registrations.

	 */

	if (fs_name_to_handle(fs_info->vfs_info.name, false)) {

		/*

		 * We already register a fs like this.

		 */

		dprintf("FS is already registered.\n");

		fibril_dec_sercount();

		futex_up(&fs_head_futex);

		free(fs_info);

		ipc_answer_0(callid, EEXISTS);

		ipc_answer_0(rid, EEXISTS);

		return;

	}

	/*

	 * Add fs_info to the list of registered FS's.

	 */

	dprintf("Inserting FS into the list of registered file systems.\n");

	list_append(&fs_info->fs_link, &fs_head);

	/*

	 * Now we want the client to send us the IPC_M_CONNECT_TO_ME call so

	 * that a callback connection is created and we have a phone through

	 * which to forward VFS requests to it.

	 */

	callid = async_get_call(&call);

	if (IPC_GET_METHOD(call) != IPC_M_CONNECT_TO_ME) {

		dprintf("Unexpected call, method = %d\n", IPC_GET_METHOD(call));

		list_remove(&fs_info->fs_link);

		fibril_dec_sercount();

		futex_up(&fs_head_futex);

		free(fs_info);

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	fs_info->phone = IPC_GET_ARG5(call);

	ipc_answer_0(callid, EOK);

	dprintf("Callback connection to FS created.\n");

	/*

	 * The client will want us to send him the address space area with PLB.

	 */

	if (!ipc_share_in_receive(&callid, &size)) {

		dprintf("Unexpected call, method = %d\n", IPC_GET_METHOD(call));

		list_remove(&fs_info->fs_link);

		fibril_dec_sercount();

		futex_up(&fs_head_futex);

		ipc_hangup(fs_info->phone);

		free(fs_info);

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/*

	 * We can only send the client address space area PLB_SIZE bytes long.

	 */

	if (size != PLB_SIZE) {

		dprintf("Client suggests wrong size of PFB, size = %d\n", size);

		list_remove(&fs_info->fs_link);

		fibril_dec_sercount();

		futex_up(&fs_head_futex);

		ipc_hangup(fs_info->phone);

		free(fs_info);

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/*

	 * Commit to read-only sharing the PLB with the client.

	 */

	(void) ipc_share_in_finalize(callid, plb,

	    AS_AREA_READ | AS_AREA_CACHEABLE);

	dprintf("Sharing PLB.\n");

	/*

	 * That was it. The FS has been registered.

	 * In reply to the VFS_REGISTER request, we assign the client file

	 * system a global file system handle.

	 */

	fs_info->fs_handle = (int) atomic_postinc(&fs_handle_next);

	ipc_answer_1(rid, EOK, (ipcarg_t) fs_info->fs_handle);

	fibril_dec_sercount();

	futex_up(&fs_head_futex);

	dprintf("\"%.*s\" filesystem successfully registered, handle=%d.\n",

	    FS_NAME_MAXLEN, fs_info->vfs_info.name, fs_info->fs_handle);

}

/** For a given file system handle, implement policy for allocating a phone.

 *

 * @param handle	File system handle.

 *

 * @return		Phone over which a multi-call request can be safely

 *			sent. Return 0 if no phone was found.

 */

int vfs_grab_phone(int handle)

{

	/*

	 * For now, we don't try to be very clever and very fast.

	 * We simply lookup the phone in the fs_head list. We currently don't

	 * open any additional phones (even though that itself would be pretty

	 * straightforward; housekeeping multiple open phones to a FS task would

	 * be more demanding). Instead, we simply take the respective

	 * phone_futex and keep it until vfs_release_phone().

	 */

	futex_down(&fs_head_futex);

	link_t *cur;

	fs_info_t *fs;

	for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {

		fs = list_get_instance(cur, fs_info_t, fs_link);

		if (fs->fs_handle == handle) {

			futex_up(&fs_head_futex);

			/*

			 * For now, take the futex unconditionally.

			 * Oh yeah, serialization rocks.

			 * It will be up'ed in vfs_release_phone().

			 */

			futex_down(&fs->phone_futex);

			/*

			 * Avoid deadlock with other fibrils in the same thread

			 * by disabling fibril preemption.

			 */

			fibril_inc_sercount();

			return fs->phone; 

		}

	}

	futex_up(&fs_head_futex);

	return 0;

}

/** Tell VFS that the phone is in use for any request.

 *

 * @param phone		Phone to FS task.

 */

void vfs_release_phone(int phone)

{

	bool found = false;

	/*

	 * Undo the fibril_inc_sercount() done in vfs_grab_phone().

	 */

	fibril_dec_sercount();

	futex_down(&fs_head_futex);

	link_t *cur;

	for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {

		fs_info_t *fs = list_get_instance(cur, fs_info_t, fs_link);

		if (fs->phone == phone) {

			found = true;

			futex_up(&fs_head_futex);

			futex_up(&fs->phone_futex);

			return;

		}

	}

	futex_up(&fs_head_futex);

	/*

	 * Not good to get here.

	 */

	assert(found == true);

}

/** Convert file system name to its handle.

 *

 * @param name		File system name.

 * @param lock		If true, the function will down and up the

 * 			fs_head_futex.

 *

 * @return		File system handle or zero if file system not found.

 */

int fs_name_to_handle(char *name, bool lock)

{

	int handle = 0;

	if (lock)

		futex_down(&fs_head_futex);

	link_t *cur;

	for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {

		fs_info_t *fs = list_get_instance(cur, fs_info_t, fs_link);

		if (strncmp(fs->vfs_info.name, name,

		    sizeof(fs->vfs_info.name)) == 0) { 

			handle = fs->fs_handle;

			break;

		}

	}

	if (lock)

		futex_up(&fs_head_futex);

	return handle;

}

/**

 * @}

 */